Carrier route record

WNSJC→SAN

Southwest Airlines · San Jose to San Diego

Flights: 3,740
Period: July 2025 to June 2026
Share of route: 75%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on SJC to SAN sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.6%. The late ones land about 45 minutes behind schedule. That rests on 3,740 flights, with a median arrival 2 minutes late.

The national on-time rate over the same period is 77.6%, so Southwest on SJC to SAN runs 7 points behind the country as a whole. Across a thousand flights that is about 69 extra late arrivals.

On time

70.7%

Arrivals under 15 minutes late, of 3,697 completed flights

Avg delay

45 min

Across delayed arrivals only, not all flights

Cancelled

0.99%

National rate is 1.81%

Whole route

72.4%

Every carrier on SJC to SAN, 4,979 flights

These figures cover 3,740 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

Carrier by carrier

Southwest against every carrier on SJC to SAN

Southwest flew 3,740 of the 4,979 flights on SJC to SAN, most of the route. Its 70.7% on time is 2 points worse than the route as a whole, which runs 72.4%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from Alaska at 91.8% to Southwest at 70.7%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on SJC to SAN
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlinesthin sample	49	91.8%	63 min	0.00%	A+
SkyWest Airlines	1,166	77.1%	49 min	1.20%	B
Spirit Airlinesthin sample	24	70.8%	62 min	0.00%	C+
Southwest Airlines (this page)	3,740	70.7%	45 min	0.99%	C+

Departure window

When Southwest runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 38 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am471 flights92.5%
8am–11am821 flights82.6%
11am–2pm719 flights69.8%
2pm–5pm673 flights64.6%
5pm–8pm763 flights54.5%
8pm–5am293 flights60.3%

Scale runs 45% to 100%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 54.5% on time, against 92.5% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8am–11am window is the busiest, with 821 flights scheduled in it.

Across the year

Southwest on SJC to SAN through the year

Darker means more delays. Figures are on-time percentages.January best, June worst

June is the worst month at 52.8% on time, 30 points below January, the best at 82.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. July was the busiest month here, with 334 flights.

Across the week, Tuesday is the strongest day at 83.5% on time and Friday the weakest at 58.7%. 25 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Southwest runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 44% of the 49,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Late-arriving aircraft
44%
National Airspace System
37%
Carrier
18%
Extreme weather
0%
Security
0%

44% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 49,000 reported delay minutes here, that single category outweighs weather by 44 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 48,958 reported delay minutes.

37% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 18,000 minutes out of 49,000, against a national NAS share of 21%.

Cancellations sit at 0.99% against a national 1.81%, which is ordinary. Diversions add another 0.16%.

Connections and stage length

What a delay here costs

6.5% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about 45 minutes, which a normal layover absorbs.

At 417 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.

The return leg is a different operation and performs like one: it runs 76.0% on time across 3,741 flights, 5 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 5 points of difference.

The sample behind these figures is 3,740 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.

What to do with this

Booking Southwest on SJC to SAN

Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 82.9% on time and June 52.8%, a swing of 30 points. If the dates move at all, move them out of June before you think about anything else. 3,697 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures